Wireless communication device and wireless communication method

ABSTRACT

Provided is a wireless communication device including, in a resource block assigned from among a plurality of resource blocks arranged in a grid pattern on a time axis and a frequency axis, a wireless communication unit for not performing transmission in a non-transmission region and for performing transmission in another region in the source block, the non-transmission region being set at a boundary with an adjacent resource block in a time direction or a frequency direction.

TECHNICAL FIELD

The present disclosure relates to a wireless communication device and awireless communication method.

BACKGROUND ART

At present, the standardization of 4G wireless communication system isbeing carried out in 3GPP (Third Generation Partnership Project). The 4Gmakes it possible to use techniques such as a relay or carrieraggregation, thereby improving the maximum communication speed and thequality at cell edges. Further, it also has been studied to improve thecoverage by introducing a base station other than eNodeB (macrocell basestation), such as HeNodeB (Home eNodeB, femtocell base station, smallbase station for mobile phone) or RHH (Remote Radio Head).

In such a wireless communication system, user equipments areframe-synchronized with a base station based on a synchronization signaltransmitted from the base station, and then an internal oscillator ofthe user equipment is synchronized with an oscillator of the basestation with high accuracy. Then, the user equipment periodicallyreceives signals transmitted from the base station and causes theinternal oscillator of the user equipment to be matched to theoscillator of the base station.

If there is any discrepancy between the internal oscillator of the userequipment and the oscillator of the base station, then reception andtransmission may not be performed at an accurate frequency and time, andthus the accuracy of the internal oscillator of the user equipment isimportant. Further, the structure of a frame that a base station shareswith user equipments is described, for example, in Patent Literature 1.

In order for a base station to simultaneously receive wireless signalstransmitted from a plurality of user equipments, each of the userequipments performs an adjustment to the length of time according to thedistance between the base station and the user equipment, which iscalled Timing Advance. Specifically, the Timing Advance is performed inthe procedure of random access in which the user equipment transmits apreamble toward a random access window. A Timing Advance value can beobtained from a relationship between an arrival time of the preamble ata base station and the random access window.

Meanwhile, there has been a discussion concerning the MTC (Machine TypeCommunications) in 3GPP. As an application of MTC, a variety ofapplications such as Metering for collecting information relevant towater systems or power systems, Health for collecting informationrelevant to health care instruments, or the like have been studied. TheMTC terminal is a terminal designed specifically for these applications.

Furthermore, the MTC terminal has characteristics such as TimeControlled, Online Small Data Transmission, for example. That is, it isexpected that the MTC terminal is kept in an idle mode for a largeamount of time, and receives signals from a base station or transmitssmall pieces of information to a base station in a burst manner. Inaddition, because low power consumption is required for the MTCterminal, it is desirable to keep the length of time taken up by theburst transmission and reception as short as possible. Further, it isconsidered that the burst transmission and reception are performed in avery long period of interval once every few hours or once every fewdays, not a period of the order of a few ms or tens of ms at which anexisting LTE terminal receives a paging channel.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2000-013870A

SUMMARY OF INVENTION Technical Problem

However, considering that the MTC terminal may not receive signals froma base station over a long period of time as described above, errors ofan internal oscillator of the MTC terminal, the frame synchronization,or the like will be increased. As a result, it is concerned that theaccuracy of uplink and downlink communications would be decreased.

Therefore, the present disclosure provides a novel and improved wirelesscommunication device and wireless communication method, capable ofsuppressing loss of communication accuracy while reducing powerconsumption.

Solution to Problem

According to an embodiment of the present disclosure, there is provideda wireless communication device including in a resource block assignedfrom among a plurality of resource blocks arranged in a grid pattern ona time axis and a frequency axis, a wireless communication unit for notperforming transmission in a non-transmission region and for performingtransmission in another region in the source block, the non-transmissionregion being set at a boundary with an adjacent resource block in a timedirection or a frequency direction.

The wireless communication device may further include a control unit forsetting the non-transmission region in the resource block.

The control unit may set the non-transmission region at a boundary withat least one of an adjacent resource block in a front side on the timeaxis or an adjacent resource block in a rear side on the time axis andat a boundary with at least one of an adjacent resource block in anupper side on the frequency axis or an adjacent resource block in alower side on the frequency axis.

The control unit may set the non-transmission region having a wider areaon the resource block as an elapsed time from a synchronizationprocessing with a communication counterpart becomes increased.

The wireless communication unit may set a length of a guard intervalpart with respect to a length of a data part in each of the Ofdm symbolsconstituting the resource block to be longer than a length defined inLTE.

The wireless communication unit may set the guard interval part in eachof the Ofdm symbols to be longer than the data part.

The wireless communication unit may use a region for transmission ofeach of a plurality of Ofdm symbols as one guard interval part and onedata part.

The wireless communication unit may set the guard interval part to belonger than the data part.

Further, according to an embodiment of the present disclosure, there isprovided a wireless communication method including in a resource blockassigned from among a plurality of resource blocks arranged in a gridpattern on a time axis and a frequency axis, not performing transmissionin a non-transmission region and performing transmission in anotherregion in the resource block, the non-transmission region being set at aboundary with an adjacent resource block in a time direction or in afrequency direction.

Further, according to an embodiment of the present disclosure, there isprovided a wireless communication device including a wirelesscommunication unit for transmitting a wireless signal in a resourceblock assigned from among a plurality of resource blocks arranged in agrid pattern on a time axis and a frequency axis. The wirelesscommunication unit transmits a reference signal at a head of theresource block at a frequency used to transmit the reference signal inthe resource block, and transmits another wireless signal aftertransmitting the reference signal.

The wireless communication unit may transmit the reference signal at allfrequencies used for transmission in the resource block.

Further, according to an embodiment of the present disclosure, there isprovided a wireless communication method including assigning a resourceblock from among a plurality of resource blocks arranged in a gridpattern on a time axis and a frequency axis, and transmitting areference signal at a head of the resource block at a frequency used totransmit the reference signal in the resource block, and transmittinganother wireless signal after transmitting the reference signal.

Advantageous Effects of Invention

As described above, according to a wireless communication device and awireless communication method related to the present disclosure, it ispossible to suppress loss of communication accuracy while keeping powerconsumption low.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram illustrating an exemplary configurationof a wireless communication system.

FIG. 2 is an explanatory diagram illustrating a frame format of 4G

FIG. 3 is an explanatory diagram illustrating resource blocks.

FIG. 4 is an explanatory diagram illustrating a problem based on anerror of an internal oscillator of the MTC terminal, framesynchronization, or the like.

FIG. 5 is an explanatory diagram illustrating a configuration of aneNodeB according to an embodiment of the present disclosure.

FIG. 6 is an explanatory diagram illustrating a setting example of anon-transmission region.

FIG. 7 is an explanatory diagram illustrating another setting example ofthe non-transmission region.

FIG. 8 is an explanatory diagram illustrating a normal arrangementposition of a reference signal.

FIG. 9 is an explanatory diagram illustrating an arrangement example ofthe reference signal according to the embodiment of the presentdisclosure.

FIG. 10 is an explanatory diagram illustrating an example of a guardinterval.

FIG. 11 is an explanatory diagram illustrating an example of a guardinterval.

FIG. 12 is an explanatory diagram illustrating an example of a guardinterval.

FIG. 13 is a flowchart showing an operation of an eNodeB according tothe embodiment of the present disclosure.

FIG. 14 is an explanatory diagram illustrating a configuration of a MTCterminal according to the embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

Also, in the specification and drawings, a plurality of structuralelements having substantially the same functional configuration may bedistinguished from each other by each having a different alphabeticalletter added to the end of the same reference numeral. For example, aplurality of structural elements having substantially the samefunctional configuration may be distinguished from each other asnecessary, such as MTC terminals 20A, 20B, and 20C. However, if it isnot particularly necessary to distinguish each of a plurality ofstructural elements having substantially the same functionalconfiguration, only the same reference numeral is assigned. For example,if it is not particularly necessary to distinguish between the MTCterminals 20A, 20B, and 20C, they are simply referred to as the MTCterminal 20.

Furthermore, “Description of Embodiments” will be described according tothe following item order.

1. Overview of Wireless Communication System

-   -   1-1. Configuration of Wireless Communication System    -   1-2. Frame Synchronization    -   1-3. Timing Advance    -   1-4. MTC Terminal

2. Configuration of eNodeB

-   -   (Setting of Non-transmission Region)    -   (Reference Signal for MTC)    -   (Guard Interval for MTC)

3. Operation of eNodeB

4. Configuration of MTC Terminal

5. Conclusion

1. Overview of Wireless Communication System

At present, the standardization of 4G wireless communication system isbeing carried out in 3GPP. Embodiments of the present disclosure, as anillustrative example, are applicable to the 4G wireless communicationsystem, and thus overview of 4G wireless communication system will befirst described.

[1-1. Configuration of Wireless Communication System]

FIG. 1 is an explanatory diagram illustrating an exemplary configurationof a wireless communication system 1. As shown in FIG. 1, the wirelesscommunication system 1 includes an eNodeB 10, a core network, MTCterminals 20, and a MTC server 30. The core network includes a MME(Mobility Management Entity) 12, an S-GW (Serving Gateway) 14, and a PDN(Packet Data Network)-GW 16.

Embodiments of the present disclosure are applicable to a wirelesscommunication device such as an eNodeB 10 and a MTC terminal 20 shown inFIG. 1. However, the eNodeB 10 and the MTC terminal 20 are merely oneexample of a wireless communication device, and the embodiments of thepresent disclosure are applicable to a variety of other wirelesscommunication devices. Examples of other wireless communication devicesinclude a user equipment (UE: User Equipment), a relay node which relayscommunications between a user equipment (MTC terminal 20) and an eNodeB,a Home eNodeB which is a small base station for home, and so on.

The eNodeB 10 is a radio base station that communicates with the MTCterminal 20. Note that only one eNodeB 10 is shown in FIG. 1, but inpractice a plurality of eNodeBs can be connected to the core network. Inaddition, although the illustration is omitted from FIG. 1, the eNodeB10 is also communicated, for example, with user equipments.

The MME 12 is a device that controls the setup, opening and handover ofsessions for data communication. The MME 12 is connected to the eNodeB10 through an interface called X2.

The S-GW 14 is a device that performs the routing, transfer, and so on,of user data. The PDN-GW 16 acts as a connection point to IP servicenetwork and transfers user data from and to the IP service network.

The MTC terminal 20 is a terminal designed specifically for applicationsfor MTC which has been studied in 3GPP and performs a wirelesscommunication with the eNodeB 10 depending on the applications. Inaddition, the MTC terminal 20 performs a bidirectional communicationwith the MTC server 30 through the core network. A user executes aparticular application by accessing the MTC server 30. The user normallydoes not directly access the MTC terminal 20. This MTC terminal 20 willbe described in detail in “1-4. MTC Terminal”.

[1-2. Frame Synchronization]

It is expected that, though the details are not provided, the eNodeB 10and the MTC terminal 20 described above will perform the wirelesscommunication in a way similar to the communication between the eNodeB10 and the user equipment. Therefore, a radio frame which is sharedbetween the eNodeB 10 and the user equipment and the framesynchronization will be described below. The details described below canbe incorporated into the communication between the eNodeB 10 and the MTCterminal 20.

FIG. 2 is an explanatory diagram illustrating a frame format of 4G. Asshown in FIG. 2, a radio frame of 10 ms is composed of 10 subframes #0to #9, each 1 ms long. Each subframe of 1 ms is composed of two slots of0.5 ms each. In addition, each slot of 0.5 ms is composed of 7 Ofdmsymbols.

Further, in the Ofdm symbols drawn with a diagonal line through it asshown in FIG. 2, synchronization signals used for frame synchronizationby the user equipment are transmitted. More specifically, a secondarysynchronization signal is transmitted in the fifth Ofdm symbol ofsubframe #0, a primary synchronization signal is transmitted in thesixth Ofdm symbol of subframe #0, a secondary synchronization signal istransmitted in the fifth Ofdm symbol of subframe #5, and a primarysynchronization signal is transmitted in the sixth Ofdm symbol ofsubframe #5.

The user equipment acquires a period of 5 ms by using the primarysynchronization signal, and at the same time, detects a cell numbergroup corresponding to a present location from the cell number groupswhich are divided into three groups. Subsequently, the user equipmentacquires a radio frame period (a period of 10 ms) by using the secondarysynchronization signal.

Moreover, a Zadoff-Chu sequence is used for a code sequence of thesynchronization signal. Because 168 types of coding sequences are usedin the cell number in the cell number group and two types of codingsequences are used to obtain a radio frame period, 336 types of codingsequences are prepared. The user equipment can determine whether areceived subframe is the subframe #0 or the subframe #5, based on acombination of the secondary synchronization signal transmitted in thesubframe #0 and the secondary synchronization signal transmitted in thesubframe #5.

An internal oscillator of the user equipment is synchronized with anoscillator of the eNodeB 10 with high accuracy after the user equipmentperforms frame synchronization as described above. Then, the userequipment periodically receives signals transmitted from the basestation and causes the internal oscillator of the user equipment to bematched to the oscillator of the base station. If there is anydiscrepancy between the internal oscillator of the user equipment andthe oscillator of the base station, then reception and transmission maynot be performed at an accurate frequency and time, and thus theaccuracy of the internal oscillator of the user equipment is important.

[1-3. Timing Advance]

In order for the eNodeB 10 to simultaneously receive wireless signalstransmitted from a plurality of user equipments, 4G user equipmentperforms an adjustment to the length of time according to the distancebetween the eNodeB 10 and the user equipment, which is called TimingAdvance. Specifically, the Timing Advance is performed in the procedureof random access in which the user equipment transmits a preamble towarda random access window. A Timing Advance value can be obtained from arelationship between an arrival time of the preamble at the eNodeB 10and the above-mentioned random access window.

It is conceivable that, though the details are not provided, the MTCterminal 20 also performs the Timing Advance and acquires a TimingAdvance value in a similar way to the user equipment.

[1-4. MTC Terminal]

The MTC terminal 20 is a terminal designed specifically for applicationsfor MTC which has been studied in 3GPP, as described above. Examples ofthe applications for MTC are as follows:

1. Security

2. Trcking & Tracing

3. Payment

4. Health

5. Remote Maintenance/Control

6. Metering

7. Consumer Devices

As an example, the MTC terminal 20 may be an electrocardiogram measuringdevice corresponding to “4. Health” in the list above. In this case, ifa user inputs a command for requesting the MTC server 30 to reportelectrocardiogram measurements, the MTC server 30 requests the MTCterminal 20 to report the electrocardiogram measurements, and then theelectrocardiogram measurements are reported from the MTC terminal 20 tothe MTC server 30.

As another example, the MTC terminal 20 may be a vending machinecorresponding to “3. Payment” in the list above. In this case, if a userinputs a command for requesting the MTC server 30 to report the salesvolume, the MTC server 30 requests the MTC terminal 20 to report thesales volume, and then the sales volume is reported from the MTCterminal 20 to the MTC server 30.

The characteristics of such MTC terminal 20 are described below. Inaddition, the MTC terminal 20 is not necessary to have all of thecharacteristics described below.

1. Low Mobility

2. Time Controlled

3. Time Tolerant

4. Packet Switched Only

5. Online Small Data Transmissions

6. Offline Small Data Transmission

7. Mobile Originated Only

8. Infrequent Mobile Terminated

9. MTC Monitoring

10. Offline Indication

11. Jamming Indication

12. Priority Alarm Message

13. Extra Low Power Consumption

14. Secure Connection

15. Location Specific Trigger

16. Group based MTC Features

Summarizing the above, the MTC terminal 20 has a little movement, has afew connections to the eNodeB 10 to communicate a small amount of data,and then again returns to an idle mode. Further, some amount of delay isacceptable in data communication. In addition, the MTC terminal 20requires extra low power consumption (13. Extra Low Power Consumption).

In this regard, the number of the MTC terminals 20 to be used in thefuture is expected. At present, nearly two billion and seven hundredmillion people out of the world's population of more than six billionpeople are using cellular phones. On the other hand, in the situationthat there are nearly five hundred trillion machines in the world,nearly five hundred million machines are using cellular phones as theMTC terminal 20.

That is, although the MTC terminals 20 are not yet widely used atpresent, on the order of one hundred trillion MTC terminals 20 would bemore likely to be accommodated in the cellular phones all over the worldin the future. Consequently, it is expected that an expanded number ofMTC terminals 20 would be accommodated in each eNodeB 10.

(Why the Embodiments of the Present Disclosure are Conceived)

The focus is placed on the MTC terminal 20 having characteristics suchas a Time Controlled, an Online Small Data Transmission, or the likeamong characteristics of the above-mentioned MTC terminal 20. It isexpected that such a MTC terminal 20 is kept in an idle mode for a largeamount of time, and receives signals from an eNodeB 10 or transmitssmall pieces of information to the eNodeB 10 in a burst manner. Inaddition, because low power consumption is required for the MTC terminal20, it is desirable to keep the length of time taken up by the bursttransmission and reception as short as possible. Further, it isconsidered that the burst transmission and reception are performed in avery long period of interval once every few hours or once every fewdays, not a period of the order of a few ms or tens of ms at which anexisting LTE terminal receives a paging channel.

However, considering that the MTC terminal 20 may not receive a signalfrom a base station over a long period of time as described above, thereis a problem that errors of an internal oscillator of the MTC terminal20, frame synchronization, a Timing Advance value, or the like would beincreased. As a result, it is concerned that the accuracy of uplink anddownlink communications would be decreased. The above-mentioned problemswill be described in detail below with reference to FIG. 3 and FIG. 4.

FIG. 3 is an explanatory diagram illustrating resource blocks. As shownin FIG. 3, the resource blocks are arranged in a grid pattern on afrequency direction and a time direction. In addition, the resourceblocks each consist of 12 subcarriers×7 Ofdm symbols. Also, a guardinterval is added to each head of the respective resource elementsconsisting of 1 subcarrier×1 Ofdm symbol. The eNodeB 10 can performresource allocation for each resource block.

FIG. 4 is an explanatory diagram illustrating problems based on errorsof an internal oscillator of the MTC terminal 20, frame synchronization,or the like. For example, there is considered a case where resourceblocks RB1 to RB3 are allocated for an uplink of the MTC terminal 20Aand a resource block RB4 is allocated for an uplink of the MTC terminal20B. Further, an internal oscillator of the MTC terminal 20B is assumedto have an error.

In this case, if the MTC terminal 20B transmits a wireless signal to theeNodeB 10 in the resource block RB4, as shown in FIG. 4, the wirelesssignal would be reached to the eNodeB 10 at a time and frequency notmatched to the original resource block RB4. Therefore, in the eNodeB 10,the wireless signal transmitted from the MTC terminal 20B is interferedwith a wireless signal transmitted from the MTC terminal 20A in theresource blocks RB1 to RB3. Such interference between the resourceblocks may cause a reception failure. A similar problem also occurs inthe downlink.

Therefore, the embodiments of the present disclosure have been designedby considering the above-mentioned circumstances as a problem to besolved. According to the embodiments of the present disclosure, it ispossible to suppress interference between resource blocks and theresultant loss in communication accuracy, while keeping powerconsumption low. The embodiments of the present disclosure will bedescribed in detail below.

2. Configuration of eNodeB

FIG. 5 is an explanatory diagram illustrating a configuration of aneNodeB 10 according to the embodiment of the present disclosure. Asshown in FIG. 5, the eNodeB 10 includes a wireless communication unit110, a control unit 120, and an upper layer 130.

The wireless communication unit 110 has a function as a receiver forreceiving a control signal, data, and so on from the MTC terminal 20,and a function as a transmitter for transmitting a control signal, data,and so on to the MTC terminal 20. Specifically, the wirelesscommunication unit 210 performs a wireless signal processing and anantenna signal processing such as modulation or demodulation, and amapping, de-mapping or interleaving of signals. Normal data and MTC dataare inputted and outputted between the wireless communication unit 110and the upper layer 130. The Normal data is transmitted and receivedbetween the wireless communication unit 110 and user equipments, and theMTC data is transmitted and received between the wireless communicationunit 110 and the MTC terminal 20.

In addition, the wireless communication unit 110 includes a MTCreference signal inserting section 112, a MTC guard processing section114, and a channel estimating section 116. The channel estimatingsection 116 estimates channel conditions between the eNodeB 10 and theMTC terminal 20 based on a reference signal received from the MTCterminal 20. The MTC reference signal inserting section 112 and the MTCguard processing section 114 perform an addition of a reference signalfor MTC and a guard interval for MTC when a communication counterpart isthe MTC terminal 20. The reference signal for MTC and the guard intervalfor MTC will be described in detail later.

The control unit 120 is configured to control the overall communicationof the eNodeB 10. The control unit 120 includes a scheduler 122 and anon-transmission region setting section 124. The scheduler 122 assigns aresource block to the MTC terminal 20 belonging to the eNodeB 10. TheMTC terminal 20 performs uplink or downlink communication by using theresource block assigned by the scheduler 122.

The non-transmission region setting section 124 sets a non-transmissionregion in the resource block assigned for the downlink by the scheduler122. The wireless communication unit 110 does not transmit a wirelesssignal in the non-transmission region which is set by thenon-transmission region setting section 124, but the wirelesscommunication unit 110 transmits a wireless signal only in regions otherthan the non-transmission region. The non-transmission region will bedescribed in detail below.

(Setting of Non-Transmission Region)

As described above with reference to FIG. 4, even in both of thedownlink communication and the uplink communication, interferencebetween resource blocks occurs due to errors of an internal oscillatorof the MTC terminal 20, frame synchronization, or the like. Thus, in theresource block assigned for the downlink by the scheduler 122, thenon-transmission region setting section 124 sets a non-transmissionregion at the boundary with adjacent resource blocks in at least one ofa time direction and a frequency direction.

FIG. 6 is an explanatory diagram illustrating a setting example of thenon-transmission region. In the example shown in FIG. 6, thenon-transmission region is set at the boundary with an adjacent resourceblock in the front side on the time axis of the respective resourceblocks and the boundary with an adjacent resource block in the lowerside on the frequency axis. More specifically, in the resource block 3,the non-transmission region corresponding to one resource element is setat the boundary with the adjacent resource block RB1 in the front sideon the time axis and the boundary with the adjacent resource block RB4in the lower side on the frequency axis.

With this configuration, even if a resource block to be received by theMTC terminal 20 has an error of as much as one resource element in eachof the frequency direction and the time direction, interference betweenthe resource blocks can be prevented.

For example, there is considered a case where a time-frequency region ofthe target to be received by the MTC terminal 20 assigned with theresource block RB2 is shifted from the resource block RB2 to theresource block RB1 side and to the resource block RB4 side by oneresource element each. In this case, because the resource elements ofthe resource blocks RB1 and RB4 included in the time-frequency regionwhich is the target to be received are non-transmission regions, the MTCterminal 20 can receive only the wireless signals transmitted from theeNodeB 10 in the resource block RB2.

Moreover, the resource elements in non-transmission regions which areset by the non-transmission region setting section 124 are not limitedto the example shown in FIG. 6. For example, the non-transmission regionsetting section 124 may set the non-transmission region at theboundaries with every adjacent resource block among the resource blocks.In addition, the non-transmission region setting section 124 may set aplurality of resource elements of each boundary as non-transmissionregions. Further, the non-transmission region setting section 124, asshown in FIG. 7, may set different non-transmission regions for therespective resource blocks or for the respective MTC terminals 20 usedas destinations.

FIG. 7 is an explanatory diagram illustrating another setting example ofthe non-transmission region. In the resource block RB1 shown in FIG. 7,the non-transmission region corresponding to two resource elements isset at the boundary with the adjacent resource block in the front sideof the time direction, the non-transmission region corresponding to oneresource element is set at the boundary with the adjacent resource blockRB3 in the rear side, and the non-transmission region corresponding toone resource element is set at the boundary with the adjacent resourceblock RB2 in the lower side of the frequency direction.

On the other hand, in the resource block RB2, the non-transmissionregion corresponding to one resource element is set at the boundary withthe adjacent resource block in the front side of the time direction, thenon-transmission region corresponding to four resource elements is setat the boundary with the adjacent resource block RB in the lower side ofthe frequency direction, and the non-transmission region correspondingto three resource elements is set at the boundary with the adjacentresource block RB1 in the upper side of the frequency direction.

In this way, the non-transmission region setting section 124 may setdifferent non-transmission regions for the respective resource blocks orfor the respective MTC terminals 20 used as destinations. Here, it iseffective to set a wide non-transmission region to the MTC terminal 20in which an error of an oscillator, frame synchronization, or the likeis large. Thus, the non-transmission region setting section 124 mayestimate the magnitude of the error in the MTC terminal 20 and set thenon-transmission region according to the magnitude of the error. Thisconfiguration allows degradation of throughput due to setting of thenon-transmission region which is wider than necessary to be prevented.In addition, the non-transmission region setting section 124 mayestimate, for example, the magnitude of the error using an elapsed timefrom frame synchronization by the MTC terminal 20, an elapsed time fromTiming Advance, a reception success rate, and so on.

(Reference Signal for MTC)

The MTC reference signal inserting section 112 inserts a referencesignal into the resource block assigned for the downlink to the MTCterminal 20. Prior to a detailed description of the MTC reference signalinserting section 112, an arrangement position of the reference signalto be transmitted to the MTC terminal will be described with referenceto FIG. 8.

FIG. 8 is an explanatory diagram illustrating a normal arrangementposition of the reference signal. As shown in FIG. 8, the referencesignals are usually inserted into a plurality of resource elements ofthe resource blocks in a distributed manner. User equipments obtainchannel information for receiving data by receiving the reference signalover one or more than one of resource blocks and supplementing it in afrequency direction and a time direction. Also, in the uplink, thereference signal is inserted in a manner similar to that describedabove.

However, it is not appropriate to apply such arrangement of the normalreference signal to the reference signal which is to be transmitted tothe MTC terminal 20. This because, with respect to the downlink, the MTCterminal 20 receives a resource block as soon as power is turned on, andthus it is not practical to receive a reference signal for a long timeso as to supplement channel information. Similarly, with respect to theuplink, the respective MTC terminals 20 use a resource block having anerror in the frequency direction and the time direction, and thus it isdifficult that the eNodeB 10 takes an enough time to obtain channelinformation based on the reference signal.

In view of the above circumstances, the MTC reference signal insertingsection 112 inserts the reference signal intensively into the head ofthe resource block assigned for the downlink to the MTC terminal 20.This will be described in detail below with reference to FIG. 9.

FIG. 9 is an explanatory diagram illustrating an arrangement example ofthe reference signal according to the embodiment of the presentdisclosure. As shown in FIG. 9, the MTC reference signal insertingsection 112 inserts the reference signal into heads of all frequenciesto be used for transmission in the respective resource blocks. Inaddition, if the non-transmission region is set as shown in FIG. 9, theMTC reference signal inserting section 112 inserts the reference signalinto directly next to the non-transmission region. If thenon-transmission region is not set, the MTC reference signal insertingsection 112 inserts the reference signal into the head of the resourceblock.

With this configuration, the early reception of the reference signal atall frequencies is possible, thus it is expected to reduce time requiredfor the MTC terminal 20 to obtain channel information. In addition, theexample that the MTC reference signal inserting section 112 inserts thereference signal into all frequencies has been described above, but thereference signal may be inserted into some frequencies rather than allfrequencies.

(Guard Interval for MTC)

The MTC guard processing section 114 adds a guard interval to an Ofdmsymbol which is to be transmitted to the MTC terminal 20 and extractsdata from the Ofdm symbol received from the MTC terminal 20. Prior to adetailed description of the MTC guard processing section 114, the guardinterval of a normal Ofdm symbol to be transmitted to a user equipmentwill be described.

The Ofdm symbol consists of a guard interval and data, as shown in FIG.3. A normal guard interval is designed to be longer than the delay timeof the reflected wave having the slowest arrival time to the direct waveso as to suppress the influence due to a multi-path. When a certainlength of signal is extracted from the Ofdm symbol composed by the guardinterval and data, it is known that data can be correctly decoded.

However, because the frame synchronization in a time direction isexpected to be incomplete in the MTC terminal 20, it is difficult forthe both eNodeB 10 and MTC terminal 20 to accurately extract signalsfrom the received Ofdm symbol in a normal guard interval.

In view of above circumstances, the MTC guard processing section 114sets the guard interval to be longer than a normal length defined inLTE. For example, the MTC guard processing section 114 sets the lengthof the guard interval to be longer than data, as shown in the lowerportion of FIG. 10. With this configuration, the tolerance of an errorrelated to the position at which the signal is extracted in the MTCterminal 20 is significantly increased, and thus it is possible toimprove a reception success rate.

More specifically, the ratio of the guard interval length to the datalength may be set 80% to 20%. With this configuration, the MTC terminal20 extracts the signal from the center of the Ofdm symbol as shown inFIG. 11, and thus if the error of frame synchronization of the MTCterminal 20 is within the range of −40% to 40% of Ofdm symbol length,the data can be decoded correctly. In this way, in addition to settingof the non-transmission region, the guard interval is set to be longer,thereby preventing interference between the resource blocks andinterference between the Ofdm symbols.

Furthermore, the MTC guard processing section 114 may estimate themagnitude of the error in the MTC terminal 20 and set the length of theguard interval according to the magnitude of the error, as similar tothe width of the non-transmission region. This configuration allowsdegradation of throughput due to setting of the non-transmission regionwhich is wider than necessary to be prevented. In addition, as amodified example shown in FIG. 12, the transmittable region of aplurality of Ofdm symbols may be used as a one part of the guardinterval and as a one part of data. With this configuration, it ispossible to further lengthen the guard interval.

3. Operation of eNodeB

The configuration of the eNodeB 10 according to the embodiment of thepresent disclosure has been described above. Next, with reference toFIG. 13, an operation of the eNodeB 10 according to the embodiment ofthe present disclosure will be described.

FIG. 13 is a flowchart showing an operation of the eNodeB 10 accordingto the embodiment of the present disclosure. As shown in FIG. 13, thescheduler 122 of the eNodeB 10 performs a scheduling of the resourceblock for the respective MTC terminals 20 (S310). Then, thenon-transmission region setting section 124 sets a non-transmissionregion in the resource block assigned for the downlink by the scheduler122 (S320). In this case, in the resource block assigned for thedownlink by the scheduler 122, the non-transmission region settingsection 124 sets the non-transmission region at the boundary with anadjacent resource block in at least one of the time direction and thefrequency direction.

Further, the MTC reference signal inserting section 112 inserts areference signal into the head of the resource block, and the MTC guardprocessing section 114 adds a guard interval longer than that defined inLTE to respective Ofdm symbols (S330). Subsequently, the wirelesscommunication unit 110 transmits the signal obtained in S330 in a regionother than the non-transmission region (S340).

4. Configuration of MTC Terminal

The configuration and operation of the eNodeB 10 according to theembodiment of the present disclosure have been described above. Next,the MTC terminal 20 according to the embodiment of the presentdisclosure will be described. The MTC terminal 20 according to theembodiment of the present disclosure, as similar to the eNodeB 10, doesnot perform any transmission in the non-transmission region, and performa transmission of a reference signal to the head of the resource block.Also, The MTC terminal 20 lengthens a guard interval, thereby preventinginterference between the resource blocks and between the Ofdms. Theconfiguration of such MTC terminal 20 will be described in detail below.

FIG. 14 is an explanatory diagram illustrating a configuration of theMTC terminal 20 according to the embodiment of the present disclosure.As shown in FIG. 14, the MTC terminal 20 according to the embodiment ofthe present disclosure includes a wireless communication unit 210, acontrol unit 220, and an upper layer 230.

The wireless communication unit 210 functions as a receiver forreceiving a control signal, data, and so on from an eNodeB 10, andfunctions as a transmitter for transmitting a control signal, data, andso on to the eNodeB 10. Specifically, the wireless communication unit210 performs a wireless signal processing and an antenna signalprocessing such as modulation or demodulation, and a mapping, de-mappingor interleaving of signals. MTC data which is transmitted and receivedbetween the wireless communication unit 210 and the eNodeB 10 isinputted and outputted between the wireless communication unit 210 andthe upper layer 230.

In addition, the wireless communication unit 210 includes a MTCreference signal inserting section 212, a MTC guard processing section214, and a channel estimating section 216. The channel estimatingsection 216 estimates channel conditions between the eNodeB 10 and theMTC terminal 20 based on a reference signal received from the eNodeB 10.

The MTC reference signal inserting section 112 has a configurationsubstantially similar to the MTC reference signal inserting section 212of the eNodeB 10. For example, the MTC reference signal insertingsection 112 inserts the reference signal into the head of all or part ofthe frequencies of resource blocks for the uplink as shown in FIG. 9.With this configuration, it is expected to reduce time required for theeNodeB 10 which is an uplink receiving side to obtain channelinformation.

The MTC guard processing section 214 has a configuration substantiallysimilar to the MTC guard processing section 114 of the eNodeB 10. Forexample, the MTC guard processing section 214 makes the length of theguard interval longer than data, as shown in FIG. 10. With thisconfiguration, the tolerance of an error related to the framesynchronization of the MTC terminal 20 is significantly increased, andthus it is possible to improve a reception success rate by the eNodeB10.

The control unit 220 is configured to control the overall communicationof the MTC terminal 20. The control unit 220 controls, for example,uplink and downlink communications by the MTC terminal 20 according toscheduling information received from the eNodeB 10.

Furthermore, the control unit 220 controls the wireless communicationunit 210 to transmit a wireless signal in a region other than thenon-transmission region, in the case where the eNodeB 10 sets thenon-transmission region to the resource block for the uplink assigned bythe eNodeB 10. In addition, the wireless communication unit 210 performsa receiving process for all of the assigned resource blocks in thedownlink.

Moreover, the control unit 220 may have a configuration substantiallysimilar to the non-transmission region setting section 124 of the eNodeB10. That is, the control unit 220 sets the non-transmission region to aresource block for the uplink assigned by the eNodeB 10.

In this way, the interference between resource blocks in the eNodeB 10can be prevented by setting the non-transmission region to the resourceblock for the uplink. In addition, the control unit 220 may estimate themagnitude of the error of a frequency, time, or the like in the MTCterminal 20 and set the non-transmission region according to themagnitude of the error. For example, the control unit 220 may set thenon-transmission region to be wide as the error of the MTC terminal 20becomes large, and may set the non-transmission region to be narrow asthe error of the MTC terminal 20 becomes small. This configurationallows degradation of throughput due to setting of the non-transmissionregion which is wider than necessary to be prevented. In addition, thecontrol unit 120 may estimate, for example, the magnitude of the errorin which the MTC terminal 20 contains by using an elapsed time fromframe synchronization by the MTC terminal 20, an elapsed time fromTiming Advance, a reception success rate, and so on.

5. Conclusion

As described above, according to the embodiments of the presentdisclosure, even if there is an error in frame synchronization,frequency, or the like of the MTC terminal 20, interference betweenresource blocks can be prevented by setting the non-transmission region.In addition, according to the embodiments of the present disclosure,interference between Ofdm symbols also can be prevented by lengthening aguard interval. Thus, the number of communication times performed by theMTC terminal 20 to adjust frame synchronization or frequency can besuppressed, thereby reducing power consumption of the MTC terminal 20.In addition, according to the embodiments of the present disclosure, itis expected to reduce time required for a receiving device to obtainchannel information by inserting a reference signal intensively into thehead of the resource block.

The preferred embodiments of the present disclosure have been describedabove with reference to the accompanying drawings, whilst the presentdisclosure is not limited to the above examples, of course. A personskilled in the art may find various alternations and modificationswithin the scope of the appended claims, and it should be understoodthat they will naturally come under the technical scope of the presentdisclosure.

Furthermore, a computer program for causing hardware such as CPU, ROMand RAM, embedded in the eNodeB 10 and the MTC terminal 20 to realize anequivalent function as each element of the above-mentioned eNodeB 10 andMTC terminal 20 can also be created. Moreover, a storage medium havingthe computer program stored thereon is also provided.

REFERENCE SIGNS LIST

-   10 eNodeB-   12 MME-   14 S-GW-   16 PDN-GW-   20 MTC terminal-   30 MTC server-   110, 210 Wireless communication unit-   112, 212 MTC reference signal inserting section-   114, 214 MTC guard processing section-   116, 216 Channel estimating section-   120, 220 Control unit-   122 Scheduler-   124 Non-transmission region setting section-   130, 230 Upper layer

The invention claimed is:
 1. A wireless communication device comprising:a wireless communication circuitry for not performing transmission in anon-transmission region of a resource block and for performingtransmission in a transmission region of the resource block, thetransmission region being a rest of the resource block excluding thenon-transmission region of the resource block, the resource block beingassigned from among a plurality of resource blocks arranged in a gridpattern on a time axis and a frequency axis, and a resource allocationbeing performed for each of the plurality of resource blocks, thenon-transmission region being set at a boundary with an adjacentresource block in a time direction or a frequency direction, wherein thenon-transmission region is set such that the transmission region of theresource block does not contact with another transmission region of theadjacent resource block, or the non-transmission region and anothernon-transmission region of the adjacent resource block are set such thatall of the boundary between the resource block and the adjacent resourceblock is contacted by either the non-transmission region or the anothernon-transmission region of the adjacent resource block.
 2. The wirelesscommunication device according to claim 1, further comprising: a controlcircuitry for setting the non-transmission region of the resource block.3. The wireless communication device according to claim 2, wherein thecontrol circuitry sets the non-transmission region at a boundary with atleast one of an adjacent resource block in a front side on the time axisor an adjacent resource block in a rear side on the time axis and at aboundary with at least one of an adjacent resource block in an upperside on the frequency axis or an adjacent resource block in a lower sideon the frequency axis.
 4. The wireless communication device according toclaim 3, wherein the control circuitry sets the non-transmission regionhaving a wider area on the resource block as an elapsed time from asynchronization processing with a communication counterpart becomesincreased.
 5. The wireless communication device according to claim 1,wherein the wireless communication circuitry sets a length of a guardinterval part with respect to a length of a data part in each of Ofdmsymbols constituting the resource block to be longer than a lengthdefined in LTE.
 6. The wireless communication device according to claim5, wherein the wireless communication circuitry sets the guard intervalpart in each of the Ofdm symbols to be longer than the data part.
 7. Thewireless communication device according to claim 1, wherein the wirelesscommunication circuitry uses a region for transmission of each of aplurality of Ofdm symbols as one guard interval part and one data part.8. The wireless communication device according to claim 7, wherein thewireless communication circuitry sets the guard interval part to belonger than the data part.
 9. A wireless communication methodcomprising: not performing transmission in a non-transmission region ofa resource block and performing transmission, by circuitry, in atransmission region of the resource block, the transmission region beinga rest of the resource block excluding the non-transmission region ofthe resource block, the resource block being assigned from among aplurality of resource blocks arranged in a grid pattern on a time axisand a frequency axis, and a resource allocation being performed for eachof the plurality of resource blocks, the non-transmission region beingset at a boundary with an adjacent resource block in a time direction orin a frequency direction, wherein the non-transmission region is setsuch that the transmission region of the resource block does not contactwith another transmission region of the adjacent resource block, or thenon-transmission region and another non-transmission region of theadjacent resource block are set such that all of the boundary betweenthe resource block and the adjacent resource block is contacted byeither the non-transmission region or the another non-transmissionregion of the adjacent resource block.
 10. A wireless communicationdevice comprising: a wireless communication circuitry for not performingtransmission in a non-transmission region of a resource block and forperforming transmission in another region of the resource block, theresource block being assigned from among a plurality of resource blocksarranged in a grid pattern on a time axis and a frequency axis, and thenon-transmission region being set at a boundary with an adjacentresource block in a time direction or a frequency direction; and acontrol circuitry for setting the non-transmission region in theresource block, wherein the control circuitry sets the non-transmissionregion at a boundary with at least one of an adjacent resource block ina front side on the time axis or an adjacent resource block in a rearside on the time axis and at a boundary with at least one of an adjacentresource block in an upper side on the frequency axis or an adjacentresource block in a lower side on the frequency axis, and the controlcircuitry sets the non-transmission region having a wider area on theresource block as an elapsed time from a synchronization processing witha communication counterpart becomes increased.